Hydraulic ram



Dec. 24, 1968 R. A. MADLAND HYDRAUL I C RAM Filed April 18, 1966 INVENIOR ROLF A. MADLAND Z W 6%, #W

ATTORNEY United States Patent 3,417,670 HYDRAULIC RAM Rolf A. Madland, Arlington Heights, 111., assignor to Parker-Hannifin Corporation, Cleveland, Ohio, :1 corporation of Ohio Filed Apr. 18, 1966, Ser. No. 543,422 3 Claims. (Cl. 92--52) ABSTRACT OF THE DISCLOSURE A telescoping ram is disclosed including a plurality of coaxial piston members each including abutment means at the load end thereof for contacting one another and transmitting forces through such abutment means rather than through the length of the piston members. All but the smallest piston member includes an internally mounted sleeve maintained captive between an intermediate internal shoulder and the aforementioned abutment means for applying the force exerted by the fluid within the ram to the corresponding piston member adjacent the load end of that piston member. Each of the piston members includes an integrally formed outwardly extending member for contacting the base end of the internally mounted sleeve of the next outermost piston member.

This invention relates generally to hydraulic rams and more particularly to telescoping rams in which a plurality of coaxially mounted piston members are extended from a cylinder member to apply a force to a load coupled to the central piston member. The invention is characterized by novel hydraulic means for applying force to the piston members and by novel mechanical means for distributing the force among the piston members to reduce the stress on the central piston member which is attached to the load.

In telescoping hydraulic rams, it is necessary to attach the load to the central piston of the telescoped piston assembly thereof, for reasons which require no explanation, and in the past it has been customary to develop hydraulic pressure only on the base end of the telescoping pistons, i.e., the end of the piston within the hydraulic cylinder. In this arrangement, the full force applied to the load is transmitted through substantially the entire length of the central piston member, which must necessarily be the smallest piston member, thereby subjecting the central piston member to heavy compressive forces throughout its entire length. This condition, of course, cannot be circumvented in the fully extended position of the telescoping piston members, but it is highly desirable to distribute the load among the other piston members when they are only partially extended. This is particularly important in applications which involve a heavy load at the start of the piston movement and a decreasing load as the piston extends itself. With this type of load, it is possible to use a much smaller and lighter hydraulic ram if the load is shared by all of the piston members instead of being fully borne by the central piston member.

In accordance with this invention, the above noted objective is attained by novel hydraulic means which develop part of the hydraulic thrust against the piston members at their load ends instead of developing all of the hydraulic thrust at their base ends, and by novel mechanical means coupling the load ends of the pistons together so that they move out as a unit with the largest piston extending itself first, and the next largest extending itself after the largest has reached its limit of travel, and so on, with the smallest piston member remaining retracted until all of the other piston members have been fully extended. By this means, the force coupled between the load and the smallest pistonis distributed among the other pistons at their load ends rather than their base ends, whereby the central piston member is not required to bear the full load alone until all of the other piston mem bers have been fully extended.

Accordingly, the principal object of this invention is to provide a telescoping hydraulic ram having improved load bearing characteristics.

Another object of this invention is to provide a telescoping hydraulic ram in which a portion of the hydraulic pressure applying to the pistons thereof is applied to the load ends of the pistons to improve the load handling characteristics thereof.

Another object of this invention is to provide a telescoping hydraulic ram including mechanical means for coupling the load ends of the pistons thereof together to improve their load handling characteristics.

A further object of this invention is to provide a telescoping hydraulic ram in which the central piston member thereof is not required to carry the full load until all of the larger pistons thereof have been fully extended.

Other objects and advantages of the invention will become apparent to those skilled in the art from the following description of one specific embodiment thereof, as illustrated in the attached drawings, in which:

FIGURE 1 is a partially cut-away elevation view of one illustrative telescoping ram of this invention with the pistons thereof in their fully retracted positions;

FIGURE 2 is a sectional view taken upon the line 22 of FIGURE 1;

FIGURE 3 is a partially cut-away elevation view of the embodiment of FIGURE 1 with the pistons thereof partially extended; and

FIGURE 4 is an enlarged section of a portion of the load end of the central piston member and the next large-r piston member shown in FIGURE 1.

FIGURE 1 shows one embodiment of the invention which is adapted to be used in applications where both the base end and load end of the ram are rotated while the ram is being extended and retracted. This embodiment comprises a cylinder member 10 including a base end piece 11 which is adapted for pivot pin coupling to a base member not shown in the drawings. An opening 12 is formed in the base end of the cylinder to receive hydraulic fluid by means of standard hydraulic couplings, also not shown in the drawings. Slidably mounted within cylinder 10 are three telescoped piston members 13, 14, and 15, each of which are shown in their fully retracted position in FIGURE 1. A load end piece 16 is attached by means of screw threads to the load end of the central piston 15. Load end piece 16 is adapted for pivot pin coupling to a load member which is not shown in the drawings. In the operation of this embodiment of the invention, hydraulic pressure is applied to the interior of the ram assembly through opening 12, thereby moving the pistons toward their extended position as shown in FIG- URE 3, with the largest piston extending first, and the next largest second, and the smallest last. FIGURE 3 shows a partially extended state of the first pistons in which the largest piston has been extended its full length and the second largest piston approximately one-half its length with the smallest piston still being fully retracted. In retraction the sequence is reversed, with the smallest Q piston retracting first, and then the next largest and then the next largest.

Each of the piston members is substantially cylindrical in form with the base end thereof enlarged and fitted with a bearing ring as indicated by the numerals 17, 18 and 19 in the drawings. Bearing rings 17, 18 and 19 are adapted to permit the passage of hydraulic fluid between the exterior of the enlarged end of each piston and the interior of the member that it slidably engages in order to apply hydraulic pressure to the load ends of the pistons as well as to their base ends. Hydraulic pressure is applied to the load ends of all but the smallest piston through annular sleeves 20 and 21, which are secured within an annular recess in the interior of the load end of the pistons by means of collar members 22 and 23, which are attached by means of screw threads to the load end of their respective piston cylinder. Sleeve members 20 and 21 are fitted with packings on the inner and outer surfaces thereof to prevent the escape of hydraulic fluid, as will be described later, and collars 22 and 23 are also fitted with a packing to wipe the surface of the next smaller piston as it retracts.

Sleeve members 20 and 21 serve a three-fold purpose: first, they provide a bearing surface for the next smaller piston as it extends and retracts, secondly they provide a hydraulic abutment against which hydraulic force can be developed against the load ends of the pistons by means of hydraulic fluid admitted past bearings 18 and 19 at the base end of the pistons, and thirdly they provide -a mechanical abutment to limit the outward travel of the piston by abutting against the enlarged base ends thereof. When hydraulic fiuid under pressure is applied to the interior of the ram assembly through opening 12, this fluid presses against the base end of each of the piston members and also against the base ends of sleeves 20 and 21 which are attached to the load ends of their respective pistons. By this means, a portion of the hydraulic force applied to the pistons is developed at the load end thereof while the remainder is developed at the base end thereof. The amount of force developed at the base and load ends of the pistons will, of course, depend on the relative effective cross-sectional area against which the hydraulic pressure works at those two points. In this particular embodiment of the invention, the force developed at the load end of each piston is approximately equal to the force developed at the base end.

Referring to FIGURE 3, the effective cross-sectional depth of the base of piston 14 is indicated by the dimension A while the effective cross-sectional depth of sleeve 21 is indicated by the dimension B. Since the radius of sleeve 21 is slightly smaller than the radius of piston 14, it will not have quite as much effective area per unit of cross-sectional depth as piston 14, but with the dimension shown the two cross-sectional areas will be approximately equal. It will be apparent to those skilled in the art that the total hydraulic force developed on piston 14 will be determined by the sum of the cross-sectional areas in the indicated by dimensions A and B in FIGURE 3, and that approximately half of this total force will be developed against the end of sleeve 21 while the remainder is developed against the base end of piston 14. The force developed against the end of sleeve 21 is communicated directly to collar 23 on the load end of piston 14 rather than being transmitted down the entire length of piston 14 as has been customary in the prior art. It will be obvious to those skilled in the art that this reduces the columnar stress on piston 14 and improves its load handling characteristics. Sleeve member 20 which is attached to piston 13 acts in a similar fashion to improve the load handling characteristics of piston 13.

Another cylindrical sleeve 24 is mounted within an annular groove in the interior of cylinder 10 and secured in place by a collar 25. Sleeve 24 acts as a bearing surface for the largest piston 13 and has an abutment to limit the outward travel of piston 13, but this sleeve is obviously not a hydraulic bearing sleeve like those described above, since it is rigidly attached to the cylinder member. In FIGURE 3, the enlarged base end of piston 13 is shown abutting against the end of sleeve 24 in its limiting position. It will be obvious to those skilled in the art that the hydraulic fluid contained in the open space between sleeve 24 and the enlarged end of piston 13 bleeds out around bearing 17 as piston 13 extends.

Central piston 15 is not fitted with a sleeve as described above, for reasons which require no explanation, but since piston 15 is hollow, a large share of the hydraulic force developed on piston 15 will be developed against end piece 16 where it seals off the extreme load end of piston 15. Thus in this invention, a large portion of the hydraulic force developed on the movable piston members is applied directly to their load ends instead of being applied to the base end and then being transmitted through the entire columnar length of the pistons to their load ends. This particular feature of the invention provides a very substantial improvement in the load handling characteristics of the pistons throughout their entire length of travel.

An additional feature of the invention provides further improvement in the load handling characteristics of the pistons in their partially extended or partially retracted positon. This feature is embodied by the particular design of collar members 22 and 23, load end piece 16, and other srtuctural features as described below. Collars 22 and 23 comprise a relatively thick top piece and a relatively thick skirt depending at right angles to the top piece to provide good mechanical coupling between the top of one collar and the bottom of the skirt of the next smaller collar as best shown in FIGURE 1, where the collars are shown in physical abutment with each other. Load end piece 16 also has a relatively thick skirt portion which makes good mechanical contact with the top of collar member 23. It will be apparent to those skilled in the art that these relatively thick structures provide a good force coupling for distributing force applied to the end piece 16 among all three of the piston members 13, 14 and 15 when the collar members are in contact with each other and with load end piece 16.

When hydraulic pressure is applied to the interior of cylinder 10 through opening 12, piston members 13, 14 and 15 move outwardly as a unit with collars 22 and 23 forced against each other and against end piece 16 until the largest piston reaches the limit of its travel as shown in FIGURE 3. During this first stage of travel, the force applied from the load to load end piece 16 will be distributed among all three of the pistons 13, 14 and 15 in proportion with the amount of cross-sectional areas that each of the three pistons present to the hydraulic pressure. This, of course, depends on the dimensions of the piston members and their associated sleeve members. These dimensions can be selected by those skilled in the art in accordance with well known prior art principles to meet the specific needs of any given application of this invention.

When the largest piston member 13 reaches the limit of its travel, the enlarged end of the piston will engage the end of sleeve member 24, as shown in FIGURE 3, thus preventing further outward movement. It should be noted that the combination of sleeve member 24 and the enlarged end of piston member 13 provides a strong mechanical contact between the piston member and the cylinder wall even when the piston is extended to its full length. After piston member 13 has reached the limit of its outward travel, piston 14 begins to move outwardly as indicated in FIGURE 3, which shows piston 14 as being extended by approximately half its length. When piston 14 begins to extend, the mechanical connection between collars 22 and 23 is broken, but the mechanical connection between end piece 16 and collar 23 remains. At this stage, the load forces applied to end piece 16 will be distributed between piston members 14 and 15. When piston 14 reaches the limit of its outward travel, piston will begin to extend and at this point piston 15 will begin to support the full load. Thus during the first third of the pistons extension cycle the load is distributed among all three pistons, in the second third of the extension cycle the load is distributed between two pistons, and only in the final third of the extension cycle is the full load supported by the central piston. It will be apparent to those skilled in the art that this substantially increases the load handling characteristics of the hydraulic ram in the first two thirds of its extension cycle. It should also be noted that even in the final third of the hydraulic rams extension cycle the full force of the load is not supported by the piston 15. Since piston 15 is hollow, the hydraulic fluid in the center of piston 15 will act directly against the load end piece 16. As can beseen in FIGURE 2, the area of load end piece 16 exposed to a hydraulic fluid is much larger than the effective cross-sectional area of piston 15, which 'means that only a small portion of the load will be borne by compressive stresses in piston 15. The shear component of the load, however, will be borne entirely by piston 15 when it is extended, so that piston 15 must be strong enough to withstand he full shear forces developed in the full extended position of the hydraulic ram.

The above described hydraulic ram can be made with any suitable prior art material by any suitable prior art techniques, many of which are well known to those skilled in the art. The dimensions of the novel sleeve members and collar members of this invention can be computed in light of the foregoing description by well known prior art formulas for any particular embodiment of the invention. In the particular embodiment disclosed in the drawings, the sleeve members are hydraulically sealed at the base ends of their outer surface by means of O-ring seals which are indicated by the small black circles in FIGURE 1 and FIGURE 3. The sleeve members are hydraulically sealed on the load end of their inner surface by means of rectangular packing elements which fit into an inner annular recess in the load ends of each sleeve member. This packing is most clearly shown in FIGURE 4, where the packing for sleeve member 21 is indicated by the numeral 26. End piece 16 is also hydraulically sealed by an O-ring, as best shown in FIGURE 4, and each of the collar elements are also sealed by flexible packings which act both as hydraulic seals and as wipers for their respective piston members. This packing is most clearly shown in FIGURE 4, where the numeral 27 designates the packing ring for collar 24. Packing 27 is shown distended due to hydraulic pressure from the rear. It will be apparent to those skilled in the art that this pressure serves to improve the seal provided by packing member 27.

In addition to the above noted advantages, the hydraulic ram of this invention also has the advantages of being simple in structure, very easy to assemble, and very sturdy in construction.

What is claimed is:

1. A hydraulic ram comprising a hollow cylinder member having a closed end and an open end, a plurality of telescoping piston members coaxially mounted within the cylinder for sliding movement relative to said cylinder and to each other, each of said piston members having a base end directed toward the closed end of said cylinder and a load end opposing said base end, each of said piston members having a different diameter, means for introducing hydraulic fluid into said cylinder member, fluid abutment means on each of said piston members for producing a force directed along the common axis of said piston members toward the load end thereof in response to pressure applied to a hydraulic fluid within said cylinder and including sleeve members attached to the interior and near the load end of each of the piston members except the smallest thereof, first mechanical abutment means near the load end of each of said piston members except the smallest for transmitting said force to the load end of the next smallest piston member including first collar members attached to the load end of said piston members except the smallest, each of said collar members having a substantially thick circular top piece with a substantially thick cylindrical skirt depending at right angles therefrom, said top piece having a lower interior surface covering and contacting the load end of the corresponding piston and sleeve member therewithin, and said skirt encircling the exterior of said piston near the load end thereof, said top piece being adapted to receive a force from the corresponding piston member and sleeve member therewithin and to transmit said force to the next smaller piston member through the skirt of the collar member attached to said next smaller piston member, said first mechanical abutment means including an exterior abutment near the load end of the smallest piston member for engaging the top piece of the collar attached to the next larger piston member, a further collar member attached to the open end of said cylinder member and having a substantially thick circular top piece adapted to engage the skirt of the collar member attached to the largest piston member, second mechanical abutment means on the exterior of the base end of each of said piston members, said second mechanical abutment means being positioned to engage the sleeve member attached to the load end of the next larger piston member to limit the sliding movement of each piston member with respect to the next larger piston member, and also including an additional sleeve member attached to the interior of said cylinder member near the open end thereof to limit the sliding movement of the largest piston member with respect to said cylinder member, the interior of the open end of said cylinder member containing an annular recess for receiving the corresponding sleeve member and a shoulder for limiting its movement toward the closed end of said cylinder, the interior of the load end of each piston member except the smallest containing an annular recess for receiving the corresponding sleeve member and a shoulder for limiting its movement toward the base end of said piston member, each of said first and further collar members being attached to their corresponding members by means of screw threads formed on the interior of said depending skirt and the exterior of the corresponding member, the top piece of each of said first and further collar members abutting against one end of the corresponding sleeve member to force the other end of said sleeve member against the corresponding shoulder, each of the piston mounted sleeve members defining an external shoulder intermediate the ends thereof in engage-' ment with said shoulder for limiting movement, first packing means mounted on said piston mounted sleeve members intermediate said external shoulder and the base end thereof and in contact with the interior surface of the corresponding member and second packing means maintained captive between said top pieces and said piston mounted sleeve member and engaging the exterior of the next smaller piston member, and bearing means attached to the exterior base end of each piston member to slidably engage the interior of the next larger member, said hearing means being adapted to permit the passage of hydraulic fluid between the base end of each piston member and the next larger member to apply hydraulic pressure to the base end of each of said sleeve members.

2. The combination defined in claim 1 wherein said second mechanical abutment means comprises an outwardly extending integral portion of the exterior of the base end of each of said piston members and defines a generally upwardly facing shoulder portion for contacting the lowermost portion of said sleeve members and an annular groove formed therein accommodating said bearing means.

3. The combination defined in claim 1 wherein each of said top pieces includes an annular groove formed therein, additional packing means mounted in each of said top piece annular grooves and contacting the exterior of the next smaller piston member.

(References on following page) References Cited UNITED STATES PATENTS 209,497 7/1957 Australia. 10/ 7 B t l 9 X 219,001 11/1958 Australia.

4,1908 22? if 92 51 X 771,282 3/1957 Great Britain. 7/1962 Wettstein 92168 X 5 7 1 75 Brinckerhoflf 91 1 9 X MARTIN P. SCHWADRON, Primary Examiner. 12/1919 Steidle 52' 115 I. C. COHEN, Assistant Examiner.

6/1929 Wirz 92-53 2/1941 Barrett 92-53 X US. Cl. X.R. 8/1957 Wilson 92 53 10 92-165, 53 10/1958 Wood et a1 9253 3/1965 Quayle 9251 8 FOREIGN PATENTS 

